| Texto completo | |
| Autor(es): |
Cunha, Antonio R.
;
Riveros, Jose M.
;
Canuto, Sylvio
;
Coutinho, Kaline
Número total de Autores: 4
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Journal of Physical Chemistry A; v. N/A, p. 13-pg., 2025-10-25. |
| Resumo | |
A correction factor for the autoprotolysis constant of methanol is proposed in the present work to obtain thermodynamic data for the standard solvation free energies of CH3OH2 + and CH3O- ions in methanol and pK a *. Using this corrected constant, K MOH *, along with known values for the standard solvation free energy of proton Delta G sol *(H+) and of the methanol molecule Delta G sol *(CH3OH), in its own liquid, in three different thermodynamic cycles, we obtain Delta G sol *(CH3OH2 +) = -91.41 +/- 2.76 kcal mol-1, Delta G sol *(CH3O-) = -88.36 +/- 2.10 kcal mol-1, and pK a *(methanol) = 22.67 +/- 2.97. To validate our approach, we applied the same thermodynamic cycles for water in its own liquid, resulting in experimental values of Delta G sol *(H3O+) = -110.20 +/- 1.91 kcal mol-1, Delta G sol *(OH-) = -104.60 +/- 0.25 kcal mol-1, and pK a(water) = 15.73 +/- 1.42. Employing quantum mechanics calculations combined with Monte Carlo simulation, we calculated the standard deprotonation free energy and the pK a values of water and methanol in their respective liquids. These calculations were performed using an explicit model of the solvent, with Free Energy Perturbation theory in Monte Carlo simulation (FEP-MC), three different pure implicit solvation models (HF-PCM, the Conductor-like Polarizable Continuum Model (C-PCM), the solvation model based on density (SMD)), and a hybrid model (cluster-SMD). Excellent agreement with experimental data was achieved using FEP-MC, HF-PCM, and cluster-SMD. Methanol is the simplest alcohol, and its pK a * value is a critical parameter in chemical and biological systems. Hence, its understanding, along with its pH* scale, enables better control and utilization of methanol in diverse applications, ranging from pharmaceuticals to industrial processes. (AU) | |
| Processo FAPESP: | 21/09016-3 - Caracterização estrutural e eletrônica de moléculas biogênicas emitidas pela flora amazônica |
| Beneficiário: | Kaline Rabelo Coutinho |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |
| Processo FAPESP: | 14/50983-3 - INCT 2014: fluidos complexos |
| Beneficiário: | Antonio Martins Figueiredo Neto |
| Modalidade de apoio: | Auxílio à Pesquisa - Temático |